Typically, an electronic system includes a number of integrated circuits that communicate with one another to perform system applications. The integrated circuits can be on the same integrated circuit chip or on separate integrated circuit chips. Often, the electronic system includes one or more host controllers and one or more electronic subsystem assemblies, such as a dual in-line memory module (DIMM), a graphics card, an audio card, a facsimile card, and/or a modem card. Typically, a DIMM includes random access memory (RAM) chips, such as double data rate dynamic random access memory (DDR-DRAM) chips. The DDR-DRAM chips can be any suitable type and generation of DDR-DRAM.
To perform system functions, the host controller(s) and subsystem assemblies communicate via communication links, such as serial communication links and parallel communication links. Serial communication links include links that implement the fully buffered DIMM (FB-DIMM) advanced memory buffer (AMB) standard or any other suitable serial communication link interface.
Integrated circuit chip speeds continue to increase and the amount of data communicated between circuits continues to increase to meet the demands of system applications. As the volume of digital data communicated between circuits continues to increase, higher bandwidth communication links are needed to prevent data communication bottlenecks between circuits and/or chips. To achieve higher speeds and optimize signal timing between circuits and/or chips, the output impedances of drivers are calibrated to targeted values. Often, common mode noise and single ended noise affect the accuracy of the calibration and produce imprecise calibrated output impedances.
For these and other reasons there is a need for the present invention.